In general, air admittance valves are used in plumbing systems as an alternative to vent systems that require venting through a complicated pipe system and/or rooftop vent system. Air admittance valves are one-way mechanical valves that may be located in a ventilated space to alleviate a need to connect to a central vertical vent (or to provide a separate vertical vent) that passes through the roof of a structure. Air admittance valves are normally closed, but open during a negative pressure condition, such as when wastewater is released. This allows air to enter the plumbing system and facilitate drainage. Once the flow of the wastewater ceases, the valve closes and remains closed until another negative pressure condition occurs. In such a manner, odors are prevented from escaping from the vent system.
Many air admittance valves are overly complex, have high part counts, and require expensive equipment and adhesives to assemble. There is a need for an improved air admittance valve that is easier and less expensive to manufacture, and that provides better performance over previous designs.